Why back button, when using the swipe back gesture is easier?
Why bookmarks button, when a tap on the address bar brings you instantly to your favorites?
Why search button, again why not just tap on the address bar?
Why tabs button, when a simple gesture (swiping up from the address bar in iOS15) can replace it?
Why is the address bar on top, when it would be more reachable on the bottom?
Every decision Apple made in iOS15 Safari is better. You just need to use it a few days to get used to it.
1. back button is faster for two hand browsing (taps are instant, swipes are not)
2. If it were hot swappable to an alternative button this wouldn't matter. They removed practically all important buttons (back button, refresh button, share button) and hid them in another convoluted scrolling menu layer; this is extremely anti productive design. E.g, switching to private tabs is now a 3 tap operation which is bogged down by a slow pop up animation for the tab menu and a slow pop in animation for the tabs themselves. Not to mention finding the private tabs button in the tab menu is significantly slower Compare this action to iOS 14: two taps that don't require anything other than muscle memory to complete as both buttons are in fixed positions. It takes me less than a second to switch between the two on iOS 14 vs. 2-3 seconds on iOS 15. That means this frequently used action takes 2-3x longer. Unacceptable for anyone that isn't a lethargic boomeresque phone/computer user.
3. for those that think having the address bar on the bottom (current iOS 15 design) is more ergonomic, two options
4. taps are instant and predictable, swiping in iOS 15 safari is not. designing to accomodate muscle memory on such a core app that people have been using for years is important.
5. because the address bar has always been at the top, where every every other browser and almost every other application (including much of Apple's own apps) display what content is currently being shown. again, why change something that isn't broken and screw with people's muscle memory.
Many of the decisions Apple made in iOS15 Safari are worse. You just need a few minutes of use to realize that. My opinion is still the same 2 weeks into using it. People have said the same thing about macOS 12's Safari too.
In conclusion: muscle memory, muscle memory, muscle memory.